Tropical Storm IN-FA Advisory Tue Jul 20

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (IN-FA) WARNING NR
016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 24.4N 130.8E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 206 NM SOUTHEAST OF KADENA AB, OKINAWA,
JAPANN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE SYSTEM
CONTINUED TO SLOWLY CONSOLIDATE AS THE CENTRAL CONVECTION DEEPENED
AND RAIN BANDS, THE LARGEST SWATH FEEDING IN FROM THE SOUTHEAST,
WRAPPED TIGHTER INTO A FORMATIVE EYE. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE FORMATIVE EYE IN THE MSI
LOOP. THE INITIAL INTENSITY OF 60 KTS IS HELD HIGHER THAN AGENCY
DVORAK AND AUTOMATED FIXES WITH HIGH CONFIDENCE BASED ON THE
IMPROVED 6-HR METSAT SIGNATURE.
INITIAL WIND RADII BASIS: PERSISTENCE  WITH SLIGHT EXTRAPOLATION
FROM PREVIOUS WIND RADII.
CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE NORTH
ANCHORED OVER JAPAN.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 39 KTS AT 192340Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: MEDIUM
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TS 09W WILL TRACK MORE WESTWARD ALONG THE
SOUTHERN PERIPHERY OF THE STR TOWARD NORTHERN TAIWAN. AFTER TAU 72,
IT WILL TURN MORE NORTHWESTWARD, NEAR TAIPEI, TAIWAN, AS IT BEGINS
TO ROUND THE WESTERN EDGE OF THE STR, THEN MAKE A FINAL LANDFALL
OVER SOUTHEAST CHINA NEAR FUZHOU NEAR TAU 108. THE FAVORABLE
ENVIRONMENT WILL PROMOTE A STEADY INTENSIFICATION TO A PEAK OF
90KTS AROUND TAU 48. AFTERWARD, INCREASING VWS AND SUBSIDENCE
ASSOCIATED WITH A MID-LATITUDE TROUGH TO THE NORTHWEST WILL
GRADUALLY WEAKEN THE SYSTEM. AFTER LANDFALL IN CHINA, LAND
INTERACTION WITH THE RUGGED TERRAIN WILL RAPIDLY ERODE THE SYSTTEM
DOWN TO 35KTS BY TAU 120.
MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT UP TO TAU
48 THEN GRADUALLY SPREAD TO JUST 90M AT TAU 72, LENDING HIGH
CONFIDENCE TO THE NEAR TO MID-TERM PORTION OF THE JTWC TRACK
FORECAST. AFTERWARD, FORECAST TRACK CONFIDENCE IS LOW AS THE MODELS
SIGNIFICANTLY DIVERGE WITH NVGM ON THE EXTREME RIGHT OF THE
ENVELOPE SUGGESTING A SHARP RECURVATURE NORTHEASTWARD, AND UKMET ON
THE LEFT MARGIN OF THE ENVELOPE WITH A FLAT WESTWARD SOLUTION
RESULTING IN A 730+ NM SPREAD.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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